Oil giant BP restarted the eastern side of the Alaskan Prudhoe Bay oil field - shut down since August when a leak was found - and expects production to reach 150,000 barrels a day by the weekend, a BP spokesman said on Wednesday.

The eastern side of the United State's largest oil field ceased production August 10, a few days after a leak was discovered in a corroded pipeline.

Initially, the company expected to shut down the west side of the field as well, but kept that side in operation after determining it could be operated safely. The west side is producing about 200,000 barrels a day.

Production in the northern part of the field adds about 50,000 barrels a day. The entire field normally produces about 450,000 barrels of petroleum products.

BP plans to replace two of three Prudhoe Bay transit lines, or about 26 km of 35 km of pipeline, because of corrosion.

The US Department of Transportation on Friday gave BP approval to resume production at three facilities on the east side of the field.

BP spokesman Daren Beaudo said the east side transit line will first be scraped and cleaned with maintenance devices known as "pigs." Within a few days, a "smart pig" that uses ultrasound will be put through the line to check for thin spots. Cleaning of the line could begin as early as this weekend, he said.

"We are resuming production in the east in a safe, orderly and structured manner," he said.

It is expected to take about a week before the east side of the field reaches a steady state of operation with production at about 150,000 barrels a day. That is still 50,000 barrels a day below pre-leak production because the line where the August leak occurred remains shut down. BP is constructing a bypass on that line.

Corrosion in the west side transit line in March resulted in a spill of up to 1,010,700 litres, the largest spill in the history of Prudhoe Bay. BP ended up putting a bypass on that line. The August leak on the east side was much smaller at about 750 litres.

Steve Marshall, the president of BP Exploration Alaska, told a congressional hearing earlier this month that full Prudhoe Bay production could be restored by late October.

BP expects to get replacement pipe by the end of the year with construction beginning early next year.